Fuel pump

It's in the gas tank. If it is easier, remove the bed to get at the tank/fuel pump assembly. If not you will have to drop the tank. Safely raise and support the vehicle. Make sure there is no pressure on the fuel system before taking fuel lines loose. Take negative battery cable loose. Drain the tank. Take electrical and fuel lines loose. The gas tank fill pipe, take it loose. Support the tank weight with some kind of floor jack. Take the tank straps loose, lower the tank, so you can get at the pump.